the debug stracktrace:

#0  0xb6d25c8b in pango_default_break (text=0x88f33c0 "", length=23, analysis=0xbfd74894, attrs=0xaaaaaaaa, attrs_len=23)
    at /build/buildd/pango1.0-1.21.3/pango/break.c:643
        type = G_UNICODE_PARAGRAPH_SEPARATOR
        break_type = <value optimized out>
        is_word_boundary = <value optimized out>
        break_op = 3218556376
        jamo = NO_JAMO
        makes_hangul_syllable = 0
        next = (const gchar *) 0x88f33c0 ""
        i = 0
        prev_wc = 0
        next_wc = 8233
        prev_jamo = NO_JAMO
        next_break_type = G_UNICODE_BREAK_MANDATORY
        prev_type = G_UNICODE_PARAGRAPH_SEPARATOR
        prev_break_type = G_UNICODE_BREAK_UNKNOWN
        prev_was_break_space = 0
        prev_GB_type = GB_Other
        prev_prev_WB_type = WB_Other
        prev_WB_type = WB_Other
        prev_WB_i = -1
        current_word_type = WordNone
        last_word_letter = 0
        base_character = 0
        sentence_state = STATE_SENTENCE_OUTSIDE
        possible_sentence_end = -1
        possible_sentence_boundary = -1
        almost_done = 1
        done = 1
        __PRETTY_FUNCTION__ = "pango_default_break"
#1  0xb6d27728 in pango_break (text=0x88f33c0 "", length=23, analysis=0xbfd74894, attrs=0xaaaaaaaa, attrs_len=23)
    at /build/buildd/pango1.0-1.21.3/pango/break.c:1697
        __PRETTY_FUNCTION__ = "pango_break"
#2  0xb6d39d39 in pango_layout_check_lines (layout=0x8d69d78) at /build/buildd/pango1.0-1.21.3/pango/pango-layout.c:3612
        delim_len = 0
        end = 0x88f33d7 ""
        delimiter_index = 23
        next_para_index = 23
        start = 0x88f33c0 ""
        done = 1
        start_offset = 0
        attrs = (PangoAttrList *) 0x8d8f090
        no_shape_attrs = (PangoAttrList *) 0x0
        iter = (PangoAttrIterator *) 0x8d8f040
        prev_base_dir = PANGO_DIRECTION_LTR
        base_dir = PANGO_DIRECTION_LTR
        state = {line_height = -1, remaining_height = -1, attrs = 0x8d8f090, items = 0x8dc5220, 
  base_dir = PANGO_DIRECTION_LTR, line_of_par = 148284928, glyphs = 0xb6bd3dc0, start_offset = -1289743872, properties = {
    uline = 148621848, strikethrough = -1076410248, rise = -1229668742, letter_spacing = -1229193228, shape_set = 0, 
    shape_ink_rect = 0x18, shape_logical_rect = 0xb6b4bd1e}, log_widths = 0x88f33c0, log_widths_offset = -1289670800, 
  line_start_index = 24, line_start_offset = -1227509772, line_width = -1227509772, remaining_width = 143602624}
        __PRETTY_FUNCTION__ = "pango_layout_check_lines"
#3  0xb6d3b13b in pango_layout_get_extents_internal (layout=0x8d69d78, ink_rect=0x0, logical_rect=0xbfd749dc, 
    line_extents=0x0) at /build/buildd/pango1.0-1.21.3/pango/pango-layout.c:2411
        line_list = <value optimized out>
        y_offset = <value optimized out>
        width = <value optimized out>
        need_width = <value optimized out>
        __PRETTY_FUNCTION__ = "pango_layout_get_extents_internal"
#4  0xb735196a in gtk_label_size_request (widget=0x8dbca10, requisition=0x8dbca2c)
    at /build/buildd/gtk+2.0-2.13.5/gtk/gtklabel.c:2521
        label = (GtkLabel *) 0x8dbca10
        width = 0
        height = 0
        logical_rect = {x = -1229131982, y = 141880176, width = 72, height = -1221256997}
        aux_info = (GtkWidgetAuxInfo *) 0x0
#5  0xb6be01fa in g_cclosure_marshal_VOID__BOXED () from /usr/lib/libgobject-2.0.so.0
No symbol table info available.
#6  0xb6bd03e9 in ?? () from /usr/lib/libgobject-2.0.so.0
No symbol table info available.
#7  0xb6bd1ba0 in g_closure_invoke () from /usr/lib/libgobject-2.0.so.0
No symbol table info available.
#8  0xb6be8cee in ?? () from /usr/lib/libgobject-2.0.so.0
No symbol table info available.
#9  0xb6beabd6 in g_signal_emit_valist () from /usr/lib/libgobject-2.0.so.0
No symbol table info available.
#10 0xb6beaf2d in g_signal_emit_by_name () from /usr/lib/libgobject-2.0.so.0
No symbol table info available.
#11 0xb73d7188 in do_size_request (widget=0x8dbca10) at /build/buildd/gtk+2.0-2.13.5/gtk/gtksizegroup.c:620
No locals.
#12 0xb73d747f in _gtk_size_group_compute_requisition (widget=0x8dbca10, requisition=0xbfd74e44)
    at /build/buildd/gtk+2.0-2.13.5/gtk/gtksizegroup.c:820
        width = <value optimized out>
        height = <value optimized out>
#13 0xb7497893 in IA__gtk_widget_size_request (widget=0x8dbca10, requisition=0xbfd74e44)
    at /build/buildd/gtk+2.0-2.13.5/gtk/gtkwidget.c:3693
        __PRETTY_FUNCTION__ = "IA__gtk_widget_size_request"
#14 0xb731bf51 in gtk_hbox_size_request (widget=0x8dc7630, requisition=0x8dc764c)
    at /build/buildd/gtk+2.0-2.13.5/gtk/gtkhbox.c:97
        child_requisition = {width = 20, height = 20}
        box = (GtkBox *) 0x8dc7630
        child = (GtkBoxChild *) 0xb3213450
        children = (GList *) 0x0
        nvis_children = 1
#15 0xb6be01fa in g_cclosure_marshal_VOID__BOXED () from /usr/lib/libgobject-2.0.so.0
No symbol table info available.
#16 0xb6bd03e9 in ?? () from /usr/lib/libgobject-2.0.so.0
No symbol table info available.
#17 0xb6bd1ba0 in g_closure_invoke () from /usr/lib/libgobject-2.0.so.0
No symbol table info available.
#18 0xb6be8cee in ?? () from /usr/lib/libgobject-2.0.so.0
No symbol table info available.